Materials handling industries, and particularly the food processing industry, often use a device referred to as a scraped surface heat exchanger. A scraped surface heat exchanger generally features a tubular outer housing which surrounds a rotating central shaft. The rotating central shaft has hingedly connected paddles that extend angularly radially outward and contact the inside surface of the outer housing as the central shaft rotates. The outer housing has a material inlet at one end and a material outlet at the other end and the material being processed is pumped through so that it passes along the length of the heat exchanger from the inlet to the outlet.
The outer housing is typically heated or cooled so that the material will undergo a change of temperature as it passes through the scraped surface heat exchanger. Further, the paddles help agitate the material and/or scrape it off the inside surface of the heat exchanger as desired.
Since the scraped surface heat exchanger essentially has a single longitudinal rotating shaft, it is typical to suspend the shaft at each end of the housing via a roller or ball bearing arrangement at the housing at each end of the shaft and each respective end of the housing. It is typically desirable to provide a seal so that the material does not come into contact with these roller bearings. Providing such a seal between the shaft and the housing is desirable to isolate the bearings from the material so that the bearings do not become clogged, to permit lubrication of the bearings, and/or to permit cleaning of the bearings by separating the bearings from the material. Further, preventing the food product from contacting the bearings also enhances the cleanliness of the food product so that it is not contaminated by materials associated with the bearings.
The known seal arrangements for sealing between the inside of the housing and the rotating central tube have some disadvantages however. In particular the seals tend to be somewhat complex and difficult to assemble and disassemble. Also, some known arrangements require a set screw to project completely through the outer housing in order to retain some non-rotating components of the seal in place.
Accordingly, there is a need in the art for a seal and sealing method which can alleviate the above mentioned disadvantages at least to some extent, and which can in some embodiments provide desirable sealing qualities between a rotating shaft and a non-rotating housing, while being simple and easy to assemble and disassemble.